There has been a long-standing desire in the electronics packaging industry to improve the mechanical performance of lead (Pb)-free solders, which are used in both wafer-level chip-scale packaging and flip-chip devices. Prior efforts have included the trace addition or doping with various elements such as, for example, Co and Zn. Prior efforts also include studies on the influence of doping (e.g., with Ti, Fe, Co, Pt, In and Ni) on the mechanical properties of Pb-free solders.
One problem observed in existing interconnect structures is premature interconnect failure due to an individual, combination or series of mechanical damaging events such as drop shock, vibration, and shear. Prior attempts to solve this problem and increase joint mechanical strength have included the use of Pb-free solders having a lower Young's modulus and hardness to help reduce brittle interconnect fracture by making the solder more compliant (e.g., indium-based Pb-free solders, Sn—Cu Pb-free solders, or Sn—Ag—Cu alloys having lower levels of silver). These prior attempts have not satisfactorily eliminated premature interconnect failure.
Accordingly, it would be desirable to have improved joint mechanical strength when using solders to manufacture wafer-level chip-scale packages or flip-chip devices.
The exemplification set out herein illustrates particular embodiments, and such exemplification is not intended to be construed as limiting in any manner.